2 . Burning coal for energy adds planet-warming carbon dioxide(CO2) to Earth's atmosphere. As the planet heats up, experts warn that simply cutting greenhouse gas emissions（排放） will not be enough to avoid global warming. CO2 must also be remcved from the atmosphere.

Existing experimental machines that pull CO2 directly from the air are too expensive to be widely used. But a new effective technology to remove CO₂ already exists. It is not expensive and easy. It is forests. Planting trees and watching forests are effective ways to clean the air.

Forests used to cover large areas of the Appalachian Mountains in the eastern United States. In the state of West Virginia, coal mining left the land there bare, without trees. Over the years, coal mining and cutting forests took over 90 percent of the red spruce（云杉） forests.

Chris Barton works for the University of Kentucky. He started a group called Green Forests Work, aiming to put trees back on the roughly 400 , 000 hectares of land.

However, Barton explains the land has problems. "If you planted trees on these places, they just didn't grow. The ground was too hard. Water didn't infiltrate（渗透）. The trees can't root. Oxygen can't circulate in those environments. "Using heavy equipment, workers tear the ground. In this way, the trees put down roots.

Barton says not everyone believes the solution is a good idea. "We've had a lot of doubtful look at us twice from people. But after we do it, there's no question that it was the right thing to do. "And it has worked. Forests are coming back to the grounds.

Scientists say that, in West Virginia alone, restoring red spruce forests to the area could send what is equal to 56 million barrels（桶）of oil into the ground. But it will take time—a long time. Around the world, experts say, nature offers powerful tools to fight climate change. But patience is needed. Nature works, but slowly, in its own time.

5 . Bob enjoys breakfasts of caviar, swims in his own saltwater pool and receives foot massages on the beach. A comfortable life, perhaps, but you could say he deserves it: Bob serves as an ambassador for conservation(保护大使). Bob,you see,is a flamingo(火烈鸟).

Odette Doest rescued Bob in 2016,after the bird crashed into a window in Curacao and hurt his left wing. While taking care of the bird at her wildlife sanctuary(庇护所），Doest discovered that Bob previously had been trained by people: He felt at ease with people,but he suffered from bumblefoot. The foot disease would have weakened his ability to catch food in the wild.

For those reasons, Doest decided to keep him as an educational animal at her sanctuary, alongside 90 other animals. When Doest began taking Bob on her foundation's weekly visits to schools on the island,the flamingo became famous instantly.

“Bob is like the hot item-everyone likes Bob,”Doest says. That's because most people have never seen such an elegant colorful bird up close.“Just don't try to take a Bobselfie. That's not what Bob is about,” Doest says firmly.“I have Bob for students to think about nature and the environment, and how a slight change in their habits can have a big effect on nature around us.”

That could mean choosing reusable cups instead of plastic bottles or skipping the balloons at a birthday party or picking up rubbish on the beach--all things Doest says children take to heart because they're so dazzled by Bob. Many of Doest's rescued birds were caught in fishing lines. In her talks, she stressed the environmental threat caused by fishing lines, along with plastic pollution.

6 . Madrid has ordered nearly half of the private cars off the roads on Thursday to deal with the worsening air pollution, a first in Spain.

The restriction (限令) will operate between 6.30 a.m. and 9 p.m. every day. The city government said in a statement: “Vehicles with even-number registration plates (偶数牌照）will be allowed to drive around on even-number days and the rest cars on the rest days.”

The measure works when levels of harmful NO2 in the atmosphere go above 200 microgrammes in every 1 in at least two measuring stations for two days running, and if the air is unlikely to clear soon.

On Thursday, the city environment officer Ines Sabanes said the restriction would not be carried out as pollution levels had dropped by the required amount. Other measures, including a ban on street parking for non-local vehicles and reduced speed limits, will continue. There are exceptions to the restriction, such as for hybrid (混合动力的) cars, those carrying three people or more or used by disabled people. Buses, taxis and emergency vehicles are not encompassed, either. “It’s not about traffic restrictions but about the important issue of public health,” deputy mayor Marta Higueras said. “Lots of people suffer from breathing problems and are very affected by pollution.”

With 3.2 million people and 1.8 million cars, Madrid often suffers from bad pollution. The move to ban half of the cars is Level Three on a series of four measures to prevent pollution. Level Four bans taxis from the city, except those that are hybrid cars.

The previous measures carried out by the city hall draw criticism from the Popular Party(PP) which ruled Madrid for nearly a quarter of a century and governs at the national level. The PP spokesman in Madrid’s local parliament said officials should do more to encourage people to avoid using their cars rather than punish them. The previous measures were carried out by former PP leader Ana Botella just before municipal elections (市政府选举) in Many 2015.

7 . For over a month, forest fires in Indonesia spread very quickly out of control as the country suffered its worst drought(干旱) in 50 years. Within days a cloud of smog was hanging over neighboring countries including Malaysia, Singapore and Thailand.

When the smoke combined with pollution from factories and cars, it soon became poisonous(有毒的). Dangerous amounts of CO became trapped under the smog and pollution levels rose. People coughed as they left the house and their eyes watered immediately.

The smog made it impossible to see across streets and whole cities disappeared as grey soot (烟灰) covered everything. In some areas, tap water was used from high-rise city buildings to try and break up the smog.

Finally, heavy rains, which came in November, put out the fires and cleared the air. But the environmental costs and health problems will remain. Breathing problems could well increase and many non-sufferers may have difficulties for the first time. Wildlife has suffered too. In lowland forests, elephants, deer, and tigers have been driven out of their homes by smog.

But smog is not just an Asian problem. In fact, the word was first used in London in 1905 to describe the mixture of smoke and thick fog. Sometimes the smog was so thick and poisonous that people were killed by breathing problems or in accidents. About 4,000 Londoners died within five days as a result of thick smog in 1952.